Policymakers are not adequately factoring land use and human diets into climate mitigation strategies: Study

A recent study finds that governments and researchers routinely underestimate the potential for changes to land use and human diets to reduce greenhouse gas emissions and mitigate the impacts of global warming.

Published in Nature last month, the research suggests that policymakers are not adequately accounting for the amount of carbon that could be stored in forests and other natural vegetation if those lands weren’t used for producing food, and are also failing to recognize the carbon emissions that will result from increased agricultural production.

According to the study’s lead author, Tim Searchinger, a research scholar at Princeton University and a senior fellow at the World Resources Institute, these oversights on the part of climate policymakers are particularly crucial because successfully mitigating climate change will require more carbon be stored in forests and other native vegetation, even while the world will have to produce as much as 50 percent more food every year in order to feed the growing global population.

A recent study finds that governments and researchers routinely underestimate the potential for changes to land use and human diets to reduce greenhouse gas emissions and mitigate the impacts of global warming.

Published in Nature last month, the research suggests that policymakers are not adequately accounting for the amount of carbon that could be stored in forests and other natural vegetation if those lands weren’t used for producing food, and are also failing to recognize the carbon emissions that will result from increased agricultural production.

According to the study’s lead author, Tim Searchinger, a research scholar at Princeton University and a senior fellow at the World Resources Institute, these oversights on the part of climate policymakers are particularly crucial because successfully mitigating climate change will require more carbon to be stored in forests and other vegetation, even while the world will have to produce as much as 50 percent more food every year in order to feed the growing global population.

“We have to take the implications of policies for land use even more seriously than people have been doing,” Searchinger said in a statement. “The fundamental problem is that policymakers and researchers have not truly confronted the fact that global land area is limited. Using any hectare (2.47 acres) for one purpose comes at the cost of not using it for another, and these opportunity costs have not been truly accounted for. The need is to make more efficient uses of land for all purposes.”

Searchinger led an international group of researchers who attempted to determine what changes to the ways we use the land would make the biggest contribution to solving the climate crisis by increasing carbon storage while meeting the world’s food needs at the same time. But determining the most efficient ways to use land is difficult because each use has its own specific outputs, Searchinger said. “When land shifts from producing corn to growing soybeans or kumquats, or is converted to forest or pasture or growing crops for bioenergy, does that increase or decrease land use efficiency? How much corn is worth how much kumquats and how much forest?”

To answer these questions, the researchers developed a method they call the Carbon Benefits Index for estimating the average amount of greenhouse gases emitted globally by the production of each type of food. The index takes into account carbon opportunity costs, as well, factoring in the amount of carbon that would have been stored in the forests and savannas that are converted to agricultural land — the researchers say that these lost opportunities for natural carbon storage are responsible for somewhere between 20 and 25 percent of the greenhouse gases in Earth’s atmosphere.

In other words, the Carbon Benefits Index seeks to establish the climate value of, for instance, a kilogram of corn by calculating the carbon lost from vegetation and soils to make that kilogram of corn. Policymakers, farmers, and private companies can then use that information to determine whether shifting from producing one food to another or converting their fields to biofuel crops or forest restoration can generate more “carbon benefits” and thus help mitigate climate change.

Using this method, the researchers determined that diets in wealthy nations are responsible for far more greenhouse gas emissions than are usually accounted for. As an example, Searchinger and team calculated that the average European person’s diet produces 9 billion metric tons of greenhouse gases every year — which is equivalent to the greenhouse gas emissions levels “typically assigned to each European’s consumption of all goods, including energy,” the authors write in the study.

Shifting from a diet based on meat and dairy to other foods could reduce these emissions by 70 percent, the researchers report. More efficient uses of land for producing meats like beef and lamb would have substantial impacts as well; the study shows that improving grazing practices on just a single hectare of land in Brazil from poor to medium quality could boost global carbon storage as much as planting a hectare of forest in Europe or the United States.

Even some measures that aim to reduce emissions but rely on intensive use of the land, such as growing biofuel crops, need to be rethought, the researchers say, as the consumption of alternative fuels like ethanol and biodiesel contributes two to three times the greenhouse gas emissions of gasoline or diesel over timeframes of 30 years or more. Meanwhile, other solutions exist: Vehicles that run on solar-sourced electricity produce 12 percent of the greenhouse gases that result from the average use of gasoline and diesel, even if they use the inefficient batteries that are currently available.

“It is important to increase both the efficiency of production on land and the efficiency of what we consume, such as what we eat, but it’s equally important that policymakers separate their efforts to influence each,” said Searchinger. “For example, beef is climate-inefficient and people can help the planet a lot by eating less, but so long as people demand beef, farmers can also help the planet by grazing beef more efficiently. Just discouraging a farmer from efficiently producing beef would hurt the climate because some less efficient farmer would likely produce the beef anyway.”